Unsaturated fatty sulfates are excellent surfactants and are widely utilized in heavy duty detergents, light duty liquids, shampoos and other cleaning products. Certain types of unsaturated fatty sulfates, such as sodium oleyl sulfate, are especially preferred surfactants due to their solubility, foaming, detergency and mildness properties. Therefore, it would be desirable to develop a method for preparing such unsaturated fatty sulfates in an inexpensive manner, such as by using inexpensive reagents and reacting the reagents under mild reaction conditions. The sulfation of unsaturated alcohols, however, is complicated by the ease with which common sulfating agents react at the carbon-carbon double bond of the unsaturated alcohol reactant. Sulfation at the carbon-carbon double bond can result in a saturated compound which has reduced effectiveness for cleaning applications.
Processes for sulfating unsaturated fatty alcohols are known in the art. U.S. Pat. No. 2,079,347, issued May 4, 1937, to Hailwood, discloses a process for preparing unsaturated sulfate esters wherein unsaturated long-chain alcohols, or mixtures thereof, are treated with the addition product of sulfur trioxide and an amine. In the disclosed process the unsaturated long-chain alcohols are converted into their sulfuric esters, or salts thereof, without attack on their unsaturated linkages.
U.S. Pat. No. 2,099,214, issued Nov. 16, 1937, to McAllister, discloses a process for sulfating unsaturated alcohols wherein said alcohols are reacted with a reagent consisting of the addition product of sulfur trioxide and dioxane. Chlorosulfonic acid may be substituted for sulfur trioxide in preparing the addition product reactant.
U.S. Pat. No. 2,060,254, issued Nov. 10, 1936, to Siebenburger, discloses a process for reacting unsaturated fatty alcohols with the addition compound of sulfur trioxide and a liquid organic base, in the presence of excess organic base, to form sulfuric acid esters of said alcohols. The sulfuric acid esters are prepared in a condition free from other sulfonation products, such as are formed by replacement of a hydrogen atom by a SO.sub.3 H group or by addition of a sulfuric acid residue at an unsaturated linkage.
U.S. Pat. No. 2,075,914, issued Apr. 6, 1937, to Snoddy et al., discloses a process for sulfating unsaturated alcohols with reagents prepared by (a) reacting sulfur trioxide with a metal chloride, or (b) reacting chlorosulfonic acid with a metal chloride or a metal sulfate.
Processes for sulfating unsaturated fatty compounds are also known in the art. U.S. Pat. No. 2,335,193, issued Nov. 23, 1943, to Nawiasky et al., discloses a process for preparing an olefinic sulfonic acid wherein olefins are sulfonated or sulfated with the addition product of 1,4-thioxane and sulfuric acid derivatives, specifically SO.sub.3 and HSO.sub.3 Cl. In the disclosed sulfation (or sulfonation) reaction the double bond of the original olefin reactant remains unreacted.
U.S. Pat. No. 4,226,797, issued Oct. 7, 1980, to Bakker et al., discloses a process for preparing a secondary C.sub.8 -C.sub.22 monoalkyl sulfuric acid, said process comprising sulfating one or more C.sub.8 -C.sub.22 olefins with sulfuric acid in the presence of at least 15% of C.sub.8 -C.sub.22 secondary alcohols.
None of the above referenced reactions, however, facilitate the sulfation of unsaturated alcohols with an ether sulfate under mild reaction conditions while at the same time providing an unsaturated fatty sulfate product which is sulfated primarily at the hydroxyl group of the original alcohol reactant. This is desirable in that a purer product will be obtained without the discoloration experienced when sulfation occurs at other reaction sites of the molecule.
It is therefore an object of the present invention to provide a process for sulfating unsaturated fatty alcohols with an ether sulfate under mild reaction conditions to form an unsaturated sulfate compound which is sulfated primarily at the hydroxyl group of the original alcohol reactant.
This object is realized by the present invention.